1. Field of Invention
The disclosure relates to a power transformer and, in particular, to a power supply.
2. Related Art
As the popular of portable electronic devices, the applications of the adaptors or chargers with USB connectors are increasing. Regarding to the current specifications, the standard output spec of USB2.0 is 5V/0.5 A, and the standard output spec of USB3.0 is 5V/0.9 A. The output spec of the cell phone charger using USB2.0 is generally 5V/1 A, or up to 5V/2 A. Accordingly, the maximum output power of a single USB connector is about 10 W.
Besides, when the adaptor or charger uses the USB port and outputs the power voltage, it cannot provide higher power voltage/current (less than 5V, 2 A) to the external electronic device due to the limitation of the available current or voltage output (must follow the USB specifications). Thus, the application of the adaptor or charger is restricted.